Optical line terminal communication method and device with data structure

ABSTRACT

An optical line terminal (OLT) coupled to a plurality of optical network units (ONUs) through a passive optical network (PON). The OLT includes a transceiver configured to communicate via a management channel of a communication network with a plurality of OLTs. The communication includes sending or receiving a notification, wherein the notification includes the following: a source OLT identifier associated with a source OLT sending the notification, wherein the source OLT is configured to communicate over a first channel at a first wavelength of the PON; a destination OLT identifier associated with a destination OLT receiving the notification, wherein the destination OLT is configured to communicate over a second channel at a second wavelength of the PON; and an ONU identifier associated with a first ONU associated with the notification.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 15/397,410 filed on Jan. 3, 2017, which is acontinuation application of U.S. patent application Ser. No. 14/600,780filed on Jan. 20, 2015 and now U.S. Pat. No. 9,577,783 granted on Feb.21, 2017 by Futurewei Technologies, Inc. and titled “Optical LineTerminal Communication Method and Device With Data Structure,” whichclaims priority to U.S. provisional patent application No. 61/930,886filed on Jan. 23, 2014 by Yuanqiu Luo, et al., and titled “Optical LineTerminal Communication Data Structure,” all of which are incorporated byreference.

BACKGROUND

A passive optical network (PON) is one system for providing networkaccess over “the last mile.” For example, the PON is atelecommunications network that includes a point-to-multi-point (P2MP)network and is comprised of an optical line terminal (OLT) at thecentral office, an optical distribution network (ODN), and a pluralityof optical network units (ONUs) at the customer premises.

The evolution for PON includes asynchronous transfer mode PON (APON),which evolved into Broadband PON (BPON), which is backward compatiblewith APON, which is defined by the International TelecommunicationsUnion Telecommunications Standard Sector (ITU-T) G.983 standard. Othersystems include Ethernet PON (EPON) for Ethernet and internet traffic.Still other alternatives include Gigabit PONs (GPONs), defined by ITU-TG.984, which have enhanced capability compared to APONs and BPONs andare backwards compatible. The G.984 standard series defines generalcharacteristics of GPON (G. 984.1) as well as physical layerspecification (G.984.2), transmission layer specification (G.984.3), andONU management and control specification (G.984.4).

With an increasing need for open access, PON systems having multipleOLTs are appearing. A multi-OLT PON can enable a plurality of serviceproviders to share infrastructure. However, a multi-OLT PON systempresents complications in the coordination and control of the variousOLTs. Consequently, there is a need in the art for methods and apparatusfor inter-OLT communication and control.

SUMMARY

Accordingly, embodiments of the present invention provide an inter-OLTcommunication protocol to manage the discovery and transition of ONUs,especially when re-allocating an ONU across OLT ports in a time- andwavelength-division multiplexing (TWDM) PON system.

In some embodiments of the present invention, an OLT is disclosed,wherein the OLT is coupled to a plurality of ONUs through a PON. The OLTincludes a transceiver configured to communicate via a managementchannel of a communication network with a plurality of OLTs. Thecommunication includes sending or receiving a notification, wherein thenotification includes the following: a source OLT identifier associatedwith a source OLT sending the notification, wherein the source OLT isconfigured to communicate over a first channel at a first wavelength ofthe PON; a destination OLT identifier associated with a destination OLTreceiving the notification, wherein the destination OLT is configured tocommunicate over a second channel at a second wavelength of the PON; andan ONU identifier associated with a first ONU associated with thenotification.

In other embodiments, a method for handing off communications betweendevices is disclosed. The method is implemented by a source OLTcommunicatively coupled to a plurality of ONUs through a PON and isconfigured to communicate over a first channel at a first wavelength ofthe PON. The method includes providing notification to a destination OLTthat a first ONU will tune to a second channel at a second wavelengthassociated with the destination OLT over a management channel of aninter-OLT communication network. The method includes sending a “tunewavelength” message to the first ONU over said first channel instructingthe first ONU to tune to the second channel. The notification and thetune wavelength message includes a source OLT identifier associated withthe source OLT, a destination OLT identifier associated with thedestination OLT, and an ONU identifier associated with the first ONU.

In another embodiment, a method of performing a handing off process ofcommunications between devices is disclosed. The method is implementedby a destination OLT communicatively coupled to a plurality of ONUsthrough a PON, wherein the destination OLT is configured to communicateover a second channel at a second wavelength of the PON. The methodincludes receiving a notification message from a source OLT over amanagement channel of a communication network indicating that a firstONU will tune to the second channel at the second wavelength. The sourceOLT is communicatively coupled to the plurality of ONUs through the PONand is configured to communicate over a first channel at a firstwavelength of the PON. The notification message includes a source OLTidentifier associated with the OLT, a destination OLT identifierassociated with the destination OLT, and an ONU identifier associatedwith the first ONU. The method includes sending a “handoff grant”message to the first ONU over the second channel. The method includesreceiving an acknowledgment from the first ONU over the second channelindicating receipt of the handoff grant message.

These and other objects and advantages of the various embodiments of thepresent disclosure will be recognized by those of ordinary skill in theart after reading the following detailed description of the embodimentsthat are illustrated in the various drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthis specification and in which like numerals depict like elements,illustrate embodiments of the present disclosure and, together with thedescription, serve to explain the principles of the disclosure.

FIG. 1 is a block diagram of a multi-OLT PON system configured toperform a handoff operation of an ONU from one OLT to another OLTthrough inter-OLT communication, in accordance with one embodiment ofthe present disclosure.

FIG. 2 is a block diagram of an OLT configured to perform a handoffoperation of an ONU, in accordance with one embodiment of the presentdisclosure.

FIG. 3 is a diagram showing an exemplary flow of messages when handingoff an ONU from one OLT to another OLT, in accordance with oneembodiment of the present disclosure.

FIGS. 4A-B are flow diagrams illustrating exemplary processes forhanding off an ONU from one OLT to another OLT, in accordance withembodiments of the present disclosure.

FIG. 5 is a diagram showing an exemplary flow of messages whenforwarding a message directed to an ONU from a first OLT to a second OLTfor delivery to the ONU, wherein the first OLT is unable to communicatewith the ONU, in accordance with one embodiment of the presentdisclosure.

FIG. 6 is a block diagram illustrating the distribution of a masterclock to a plurality of OLTs within a central office, in accordance withone embodiment of the present disclosure.

FIG. 7 is a table illustrating exemplary ONU data elements, inaccordance with one embodiment of the present disclosure.

FIG. 8 is a table illustrating exemplary OLT data elements, inaccordance with one embodiment of the present disclosure.

FIG. 9 is a table providing exemplary state change requests andnotifications, in accordance with one embodiment of the presentdisclosure.

FIG. 10 is a table illustrating exemplary Inter-Channel TerminationProtocol (ICTP) protocol primitive invocation format elements.

FIG. 11 is a table illustrating exemplary ICTP protocol primitives.

DETAILED DESCRIPTION

Reference will now be made in detail to the various embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. While described in conjunction with theseembodiments, it will be understood that they are not intended to limitthe disclosure to these embodiments. On the contrary, the disclosure isintended to cover alternatives, modifications and equivalents, which maybe included within the spirit and scope of the disclosure as defined bythe appended claims. Furthermore, in the following detailed descriptionof the present disclosure, numerous specific details are set forth inorder to provide a thorough understanding of the present disclosure.However, it will be understood that the present disclosure may bepracticed without these specific details. In other instances, well-knownmethods, procedures, components, and circuits have not been described indetail so as not to unnecessarily obscure aspects of the presentdisclosure.

Accordingly, embodiments of the present invention provide an inter-OLTcommunication protocol to manage the discovery and transition of ONUs,especially when re-allocating an ONU across OLT ports in a TWDM PONsystem.

Some portions of the detailed descriptions which follow are presented interms of procedures, steps, logic blocks, processing, and other symbolicrepresentations of operations on data bits that can be performed oncomputer memory. These descriptions and representations are the meansused by those skilled in the data processing arts to most effectivelyconvey the substance of their work to others skilled in the art. Aprocedure, computer generated step, logic block, process, etc., is here,and generally, conceived to be a self-consistent sequence of steps orinstructions leading to a desired result. The steps are those requiringphysical manipulations of physical quantities, and refer to the actionand processes of a computing system, or the like, including a processorconfigured to manipulate and transform data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission or display devices.

Flowcharts of examples of methods for guaranteeing network controltraffic are provided, according to embodiments of the present invention.Although specific steps are disclosed in the flowcharts, such steps areexemplary. That is, embodiments of the present invention are well-suitedto performing various other steps or variations of the steps recited inthe flowcharts. Also, embodiments described herein may be discussed inthe general context of computer-executable instructions residing on someform of computer-readable storage medium, such as program modules,executed by one or more computers or other devices. By way of example,and not limitation, the software product may be stored in a nonvolatileor non-transitory computer-readable storage media that may comprisenon-transitory computer storage media and communication media.Generally, program modules include routines, programs, objects,components, data structures, etc., that perform particular tasks orimplement particular abstract data types. The functionality of theprogram modules may be combined or distributed as desired in variousembodiments.

FIG. 1 is a block diagram of a multi-OLT PON (e.g., NG-PON2) system 100configured to perform a handoff operation or “handoff” of an ONU fromone OLT to another OLT through inter-OLT communication, in accordancewith one embodiment of the present disclosure. As the PON system 100access network grows, carrier/operators need to operate and maintainmultiple OLT ports, which may require handing off ONUs from one OLT portto another. For example, carrier/operators may turn off certain OLTports to save power consumption at the central office 110, and need tohand off ONUs so that service is not interrupted. In another example,during normal operation, if an OLT port is heavily loaded with networktraffic, the corresponding OLT may perform load balancing betweenchannels and may command some of its associated ONUs to tune theirdownstream and/or upstream wavelength channels to another OLT porthaving lighter traffic.

PON system 100 is a communication network that does not require anyactive components to distribute data between the plurality of OLTs 120and the plurality of ONUs 170. For example, passive optical componentsin the ODN 160 are used to distribute data between the OLTs and theONUs. Examples of PONs suitable for implementing embodiments of thepresent invention are described within the context of the G.989 seriesof ITU-T Recommendations describing the latest or next generation ofpassive optical networks (NG-PON2) providing 40 Gigabit-capablecommunications for residential, business, mobile backhaul, and otherapplications, all of which are incorporated by reference herein as ifreproduced in their entirety. NGPON2 is based on wavelength-domainmultiplexing, and comprises channel or wavelength pairs which also usetime-domain multiple access as well as dedicated, point-to-point channelpairs. NG-PON2 variants can differ in channel bit rates, passive reach,usable wavelength ranges, and also with regard to several implementationoptions. NG-PON2 is backward compatible with G-PON and asymmetric10-gigabit PON (XG-PON1), which ensures that NG-PON2 can be used forvarious applications, such as access, backhaul and fronthaulapplications. Other PONs supporting embodiments of the present inventioninclude APON, BPON, and wavelength-division multiplexing (WDM) PON, asdefined by one or more standards.

In particular, PON system 100 may comprise a plurality of OLTs 120, inFIG. 1 represented as OLTs 1 . . . N. The plurality of OLTs 120 aremanaged within a central office 110, in one embodiment. In embodimentsof the present invention, inter-OLT communication is implemented tofacilitate the transfer of ONUs from one OLT port to another within thecentral office 110. For example, central office 110 includes aninter-OLT communication platform or management channel 140 that allowsfor communication between the plurality of OLTs 120. In one embodiment,the inter-OLT communication includes broadcasting messages from one OLTto the other OLTs in one communication. In another embodiment, theinter-OLT communication is peer-to-peer, such that one OLT cancommunicate directly with another OLT. In addition, other devices can becoupled to the communication platform 140 to allow for communicationwith the OLTs 120. For example, a separate master OLT controllerprovides for OLT management and control (e.g., providing conflictresolution between OLTs). As examples, central office 110 can be locatedin one site having local area networking, or across multiple sitescommunicating through a wide area network.

Embodiments of the present invention disclose the communication datastructure to support OLT communication, as when performing handoff ofone or more ONUs from one OLT to another. The data structure containskey information elements that are communicated among the OLT ports.Specifically, the data structure applies to system or network controland management between multiple OLT ports.

The plurality of OLTs 120 are communicatively coupled to the ODN 160through a shared infrastructure, such as multiplexer (MUX) 150. In oneembodiment, MUX 150 performs WDM. In another embodiment, MUX 150 canalso be configured to perform time division multiplexing, such that MUX150 is able to perform TWDM. For example, next generation PONtechnologies implemented in PON system 100 employ multiple wavelengthsto stack time-division multiplexing PONs (TDM-PONs) into a TWDM-PON. Assuch, each OLT port in a TWDM-PON is generally an XG-PON running on apair of downstream and upstream wavelengths. The stacked feature ofTWDM-PON provides support to the pay-as-you-grow requirement forcarriers/operators. That is, a carrier/operator can add new OLT ports inorder to scale up network performance to support new customers.

Specifically, each of the plurality of OLTs 120 operate on a differentoptical wavelength for downstream data communication (e.g., towards theONUs 170), and operate on a different wavelength for upstream datareception (e.g., from the ONUs 170). For example, each OLT can have awavelength pair of communication channels. Each OLT is coupled to arespective port of the WDM MUX 150 via separate channels 155 (e.g.,fibers). More particularly, in the downstream direction, the WDM MUX 150multiplexes optical signals from the channels 155 onto a single channel190 (e.g., optical fiber), which is delivered to the ODN. MUX 150 can bebi-directional, such that in the upstream direction, WDM MUX 150demultiplexes the signal over channel 190 by taking the single inputsignal and selecting one of the data output lines leading to acorresponding OLT (e.g., OLT port).

ODN 160 is a data distribution system that can include optical fibercables or other optical transmission medium, couplers, splitters,distributors and/or other equipment. For example, as shown in FIG. 1,ODN 160 can include a splitter 165 that copies the signal on channel 190and distributes the copied signals to the plurality of ONUs 170(numbered 1 . . . N) over a channel network 175 (e.g., fibers). Splitter165 is bi-directional, capable of combining upstream signals from theplurality of ONUs 170 into one signal transmitted over channel 190, andof copying and distributing a downstream signal from the plurality ofOLTs 120 on channel 190 to the plurality of ONUs 170 over the channelnetwork 175. In the upstream direction, signals from the ONUs 170 arecombined by a splitter into one signal before being transmitted overchannel 190. More particularly, the devices located within ODN 160 arepassive optical components that do not require any power to distributedata signals between the plurality of OLTs 120 and the plurality of ONUs170.

An ONU can be any device that is configured to communicate with acorresponding OLT, wherein the ONU is associated with a customer or user(not shown), and is typically located at the customer site. Generally,an ONU provides an intermediary or interface between a customer and anOLT. For example, the plurality of ONUs 170 can forward data receivedfrom the plurality of OLTs 120 to one or more customers. In addition,the plurality of ONUs 170 can forward data received from the customerback to the plurality of OLTs 120.

More particularly, an ONU can include an optical transmitter configuredto send optical signals to the plurality of OLTs 120, and an opticalreceiver configured to receive optical signals from the OLTs 120. Thatis, the ONU can tune to a selectable downstream wavelength and anotherselectable upstream wavelength, which forms a wavelength pair. The ONUcan include a converter that converts an optical signal into electricalsignals for the customer end, such as converting to an asynchronoustransfer mode (ATM) or Ethernet format. Further, the ONU can include asecond transmitter and/or receiver for sending and/or receiving signalsto and from the customer end.

FIG. 2 is a block diagram of an OLT 200 configured to perform handoff ofan ONU, in accordance with one embodiment of the present disclosure. Forexample, OLT 200 can be implemented within the plurality of OLTs 120 inPON system 100 of FIG. 1.

Specifically, OLT 200 (e.g., a source OLT) is coupled to a plurality ofONUs through a PON, and is configured to communicate with one or moreONUs over a first channel at a first wavelength of the PON. As a source,OLT 200 is configured to communicate with a first ONU over the firstchannel. In addition, when handing off the ONU, OLT 200 is configured toprovide a notification to the destination OLT that the ONU will tune toa second channel at a second wavelength that is associated with thedestination OLT over a management channel of an inter-OLT communicationnetwork.

It is appreciated that OLT 200 is configured to communicate informationvia a data structure supporting OLT communication. Specifically, thedata structure defines the key information entities that are needed toperform management of the OLT ports, such as when performing handoff ofone or more ONUs from one OLT to another. In one embodiment, whenperforming handoff, the data structure in the notification includes atleast: a source OLT identifier associated with the source OLT; adestination OLT identifier associated with the destination OLT; and anONU identifier associated with the ONU being handed over. Otherinformation in the data structure can also be included, as will bedescribed more fully below.

In particular, OLT 200 includes a processor 220 and memory 230, wherethe processor 220 is configured to execute computer-executableinstructions stored in the memory 220. For example, processor 220 isconfigured to perform handoff of an ONU from one OLT to another OLTthrough inter-OLT communication, or to enable communications from oneOLT to an ONU through another OLT. In one embodiment, the processor 220performs the functions of one or more of the example embodimentsdescribed and/or illustrated herein, such as the operations performed byany of the OLTs 120 in FIG. 1. Further, the processor 220 can beincluded within a single or multi-processor computing device or systemcapable of executing computer-readable instructions. In a general form,a computing device includes at least one processor and a system memory.System memory is coupled to the processor, and generally represents anytype or form of volatile or non-volatile storage device or mediumcapable of storing data and/or other computer-readable instructions.Examples of system memory include, without limitation, random accessmemory (RAM), read only memory (ROM), Flash memory, or any othersuitable memory device.

Specifically, the OLT 200 can be any device that its configured tocommunicate with a plurality of ONUs (e.g., ONUs 120 of FIG. 1 in a PON)and/or another network (not shown). That is, OLT 200 can be configuredto forward data received from the network to the plurality of ONUs, andto forward data received from the ONUs to the network. OLT 200 alsoincludes a converter that converts data received from another network toa format compatible with the plurality of ONUs located on a downstreamdirection, in one embodiment.

Downstream and upstream communications to and from OLT 200 arefacilitated through transceiver 240, such that transceiver 240 isconfigured to forward communications to ONUs and to receivecommunications from the ONUs over an ODN network coupled to port 260.Transceiver 240 is coupled to WDM 250 that acts as amultiplexer/demultiplexer when transmitting and/or receivingcommunications to and from port 260, wherein port 260 is coupled to aplurality of ONUs through a corresponding ODN, as previously described.

In one embodiment, transceiver 240 includes a medium access control(MAC) component that provides addressing and channel access controlmechanisms for a plurality of OLTs sharing a single communicationchannel in the ODN network. For example, TWDM methods allowcommunications from one or more OLTs connected to a multi-pointtransmission medium (e.g., single channel) to share its capacity (e.g.,transmit and receive). For example, one multiplexing method allowsseveral data streams to share the same physical communication channel.In one embodiment, MAC component 245 transmits Ethernet frames.

As shown in FIG. 2, OLT 200 is configured to communicate on differentoptical wavelengths for upstream and downstream traffic, which form theOLT wavelength pair. For example, in the downstream direction, OLT sendsdownstream communications on wavelength λ_(d), and receives upstreamcommunications on wavelength λ_(u). The wavelength pair, including theupstream and downstream wavelengths, can be different for each of theOLTs in a PON. As such, when handing off one ONU from one OLT toanother, the inter-OLT communications identify the wavelengths withinembodiments of the present invention.

FIG. 3 is an information flow diagram 300 showing the flow of messageswhen handing off an ONU from one OLT to another OLT, in accordance withone embodiment of the present disclosure. Specifically, the messagesshown in FIG. 3 are delivered between a source OLT, a destination OLT,and an ONU. The source OLT is handing off the transmitting (downstreammessaging) and/or receiving (upstream messaging) of messages with theONU to the destination OLT. That is, the source OLT directs an ONU totune one or more of its wavelengths to work with the port of thedestination OLT. For example, an ONU can be transferred between OLTs ofa particular carrier to perform bandwidth management. In anotherexample, an ONU can be transferred between OLT operating systemdifferent carriers because a customer is changing his or her carriernetwork. In both of these cases, the source OLT and the destination OLTare known components, and FIG. 3 illustrates the messaging performedbetween the OLTs when handing off an ONU.

In one embodiment, it is assumed that the source OLT (prior toperforming handoff of an ONU to the destination OLT) has previouslydetermined or received the necessary information contained in a datastructure to perform the handoff process, such as one or more of thefollowing: 1) a destination OLT identifier; 2) a source OLT identifier;3) an ONU identifier; 4) the current downstream wavelength/channel forthe ONU; 5) the current upstream wavelength/channel for the ONU; 6) apossible new downstream wavelength/channel for the ONU; 7) a possiblenew upstream wavelength/channel for the ONU; 8) an ONU turning starttime; and 9) an acknowledge code. In another embodiment, the informationis determined and/or communicated between the source OLT, destinationOLT, and ONU during the handoff process.

In particular, the source OLT and the destination OLT need to be able tocoordinate with one another to efficiently handle the transition of theONU from one OLT to another. During the coordination process, the sourceOLT will communicate with the destination OLT an identifier indicatingwhich ONU is going to retune. The source OLT will or has determineddetails about the destination OLT wavelength pair. The destination OLTacknowledges its readiness to receive the ONU prior to commencing thetransition. The destination OLT also acknowledges when the transition iscomplete. Each OLT has an OLT ID to uniquely identify itself in theinter-OLT communication process.

In one embodiment, some of the messages disclosed in FIG. 3 conform witha physical layer operation and an administration and maintenance (PLOAM)control message format, where the PLOAM message is a protocol used in acorresponding PON for sending messages between the OLTs and the ONUs.For example, PLOAM messaging is defined in the G.989 series of ITU-TRecommendations, previously introduced. Of course, any suitable formatused for communicating control and management messages can also be used.

As shown in FIG. 3, at 305 the source OLT sends a tune wavelengthnotification to the destination OLT. That is, the source OLT notifiesthe destination OLT that a specified ONU will change one or more of itswavelengths (upstream and/or downstream wavelengths) to those that aresupported by the destination OLT. The notification is delivered over theinter-OLT communication network, such as by broadcasting the tunewavelength notification over a management channel. OLTs are able tofilter the notification, such that only the OLT to which thenotification is directed accepts the message, where the OLTs that arenot targeted will discard the notification message. As such, at 310, thedestination OLT sends back to the source OLT an acknowledgment that thenotification has been received. In one embodiment, the destination OLTalso sends back additional information such as its upstream (e.g.,λ_(u2)) and/or downstream (e.g., λ_(d2)) wavelengths.

Once the destination OLT confirms the tune wavelength notification, at315, the source OLT sends a tune wavelength command to the ONUinstructing the ONU to tune to the new wavelength or wavelengths at aparticular time. In the example of FIG. 3, the tune wavelength commandinstructs the ONU to tune to new upstream and downstream wavelengthsassociated with the destination OLT. That is, the source OLT tells theONU to tune its current wavelength pair of λ_(u1), λ_(d1) to the newwavelength pair of λ_(u2), λ_(d2). As such, the command includes atleast the wavelength pair for the destination OLT (e.g., upstreamwavelength λ_(u2), and downstream wavelength λ_(d2)), as previouslydescribed.

Though the example provided in FIG. 3 shows that the ONU can beinstructed to tune to both the upstream and downstream wavelengthsassociated with the destination OLT, other embodiments and examplesprovide for selecting tuning, such that only the tune wavelength commandinstructs the ONU to tune to either the upstream wavelength λ_(u2), ordownstream wavelength λ_(d2). That is, the ONU will be tuning to one orboth of the upstream and downstream channels in the wavelength pair.

In addition, the tune wavelength command provides instructions as towhen to start the tuning process by including a time for the ONU tostart tuning to the new wavelength or wavelengths. For example, the PONincludes a system clock that is known to all components of the PONsystem, or at least those entities involved in the handing off process.In one embodiment, the system clock implements a super frame counter(SFC) that uses frames as a means for coordinating time. As shown, thetune wavelength command includes a tuning start time SFC_(n), whichindicates the time when the ONU should begin tuning to the newwavelength or wavelengths.

At 320 of FIG. 3, the ONU sends back an acknowledgment to the source OLTindicating receipt of the tune wavelength command. In the meantime, thesource OLT can send down SFC frame messages counting down the time tothe tuning start time SFC_(n), to include messages 325 and 330. Up tothis point, at least between messages 305 to 330, the ONU is operatingin a normal operation state in the ONU state machine.

In addition, the destination OLT knows that the ONU is tuning to itsupstream wavelength λ_(u2), and/or downstream wavelength λ_(d2)beginning with the tuning start time SFC_(n). As such, at some pointafter the tuning start time, indicated by SFC_(n), the destination OLTsends out a notify wavelength message. That is, the notify wavelengthmessage pings the ONU to acknowledge when it has completed its tuningprocess and can communicate with the destination OLT.

The destination OLT periodically sends the notify wavelength messageuntil the ONU returns an acknowledgment at 360, in one embodiment. Forexample, notify wavelength messages (e.g., 340 a-n) are delivered afterevery downstream (DS) frame interval 347, which includes one or more DSframes. In one embodiment, the notify wavelength message is broadcastedto the plurality of ONUs. In addition, up to this point at least betweenmessages 330 and 340 n, the ONU is operating in awavelength-tuning-operation state in the ONU state machine.

When the ONU successfully finishes wavelength tuning, it is able tocommunicate with the destination OLT using the upstream wavelengthλ_(u2), and/or the downstream wavelength λ_(d2). As such, the ONU isable to receive the latest notify wavelength message 340 n, and respondby sending an acknowledge message 360 back to the destination OLT. Theacknowledgment message 360 indicates that the ONU is now online usingthe new downstream and/or upstream wavelengths.

FIG. 4A is a flow diagram 400A illustrating an exemplary process forhanding off communications of at least one channel used by an ONU fromthe source OLT to a destination OLT as implemented by the source OLT, inaccordance with one embodiment of the present disclosure. In oneembodiment, flow diagram 400A is a computer implemented method forhanding off communications of at least one channel used by an ONU fromthe source OLT to a destination OLT as implemented by the source OLT. Inanother embodiment, flow diagram 400A is implemented within a computersystem including a processor and memory coupled to the processor andhaving stored therein instructions that, if executed by the computersystem cause the system to execute the method for handing offcommunications of at least one channel used by an ONU from the sourceOLT to a destination OLT as implemented by the source OLT. In stillanother embodiment, instructions for performing the method are stored ona non-transitory computer-readable storage medium havingcomputer-executable instructions for causing a computer system toperform the method for handing off communications of at least onechannel used by an ONU from the source OLT to a destination OLT asimplemented by the source OLT. The operations of flow diagram 400A areimplemented within an OLT shown in FIGS. 1 and 2, in some embodiments ofthe present disclosure. In addition, flow diagram 400A can furtherdescribe one or more operations performed during the handing off of anONU from one OLT to another as described in the information flow diagram300 of FIG. 3.

Flow diagram 400A of FIG. 4A discloses the process performed by a sourceOLT when handing off communications with an ONU to a destination OLT.That is, the source OLT is handing off the transmitting (downstreammessaging) and/or receiving (upstream messaging) of messages with theONU to the destination OLT. The source OLT is communicatively coupled toa plurality of ONUs through a PON. In particular, the source OLT isconfigured to communicate over a first channel at a first wavelength ofthe PON. The first channel can be either the downstream channel or theupstream channel.

Flow diagram 400A is performed after the source OLT determines or isinstructed to perform the handing off of one or more wavelengths used tocommunicate with an ONU. At 410, the method includes providingnotification to the destination OLT that a first ONU will tune to asecond channel at a second wavelength associated with the destinationOLT over a management channel of an inter-OLT communication network. Forexample, the source OLT can be handing off to a destination OLTdownstream communication to an ONU that is currently being handled bythe source OLT. In another example, the source OLT can be handing off toa destination OLT upstream communication with an ONU that is currentlybeing handled by the source OLT. In still another example, the sourceOLT can be handing off to a destination OLT both upstream and downstreamcommunication with an ONU that is currently being handled by the sourceOLT. An acknowledgment can also be received at the source OLT, from thedestination OLT, indicating receipt of the notification message.

In one embodiment, the notification message is broadcast to a pluralityof OLTs over a management channel. That is, the notification message isbroadcast over an inter-OLT communication platform. The OLT intended toreceive the notification message is able to determine that thenotification message is targeted to itself. For example, OLTs are ableto parse the header to determine which destination OLT should handle thenotification message.

Necessary information used for implementing the handoff is alsodetermined or provided to the source OLT. In one embodiment, the OLTidentifier (OLT-ID) provide one or more key pieces of information. Thecontent of the OLT-ID could be the PON ID specified in the ITU-TRecommendation 987.3, the channel IDs for a downstream and upstreamwavelength pair; the ID of an individual wavelength/channel; the PON TAGspecified in ITU_T Recommendation 987.3; or the ID of an OLT port, etc.

At 420, the method includes sending a tune wavelength message to thefirst ONU over the first channel instructing the first ONU to tune tothe second channel. For example, the source OLT can send a command tothe first ONU to tune to the downstream wavelength associated with thedestination OLT in order to receive data from the destination OLT. Inanother instance, the source OLT can send a command to the first ONU totune to the upstream wavelength associated with the destination OLT,such that the first ONU will now send messages to the destination OLTinstead of the source OLT. In still another instance, the source OLT cansend a command to the first ONU to tune to both the upstream and thedownstream wavelengths associated with the destination OLT, such thatthe first ONU will now only communicate with the destination OLT. Anacknowledgment can also be received at the source OLT from the ONUindicating receipt of the tune wavelength message.

In one embodiment, the tune wavelength message is broadcast to aplurality of ONUs through a corresponding ODN using a downstream channelassociated with the source OLT. This downstream channel can also behanded off, in one implementation. The ONU intended to receive thenotification message determines that the tune wavelength message istargeted to itself. For example, ONUs are able to parse the header todetermine the which destination ONU should handle the tune wavelengthmessage.

In one embodiment, the information necessary to implement a handoffincluded within the notification message and/or the tune wavelengthmessage is provided in a data structure. For example, the notificationmessage and/or tune wavelength message includes at least one of thefollowing: 1) a destination OLT identifier; 2) a source OLT identifier;and 3) an ONU identifier. In another embodiment, the notificationmessage and/or tune wavelength message includes additional information,including at least one of the following: 1) the current downstreamwavelength/channel for the ONU; 2) the current upstreamwavelength/channel for the ONU; 3) a possible new downstreamwavelength/channel for the ONU; 4) a possible new upstreamwavelength/channel for the ONU; 5) an ONU turning start time; and 6) anacknowledge code. For illustration, the data structure provided in anotification message and/or the tune wavelength message can bestructured as follows:

{ Destination OLT-ID, Source OLT-ID, ONU-ID, ONU current downstreamwavelength/channel, ONU current upstream wavelength/channel, ONU newdownstream wavelength/channel, ONU new upstream wavelength/channel, ONUtuning start time, Acknowledge code, }

FIG. 4B is a flow diagram 400B illustrating an exemplary process forhanding off communications of at least one channel used by an ONU from asource OLT to a destination OLT as implemented by the destination OLT,in accordance with one embodiment of the present disclosure. In oneembodiment, flow diagram 400B is a computer implemented method forhanding off communications of at least one channel used by an ONU fromthe source OLT to a destination OLT as implemented by the destinationOLT. In another embodiment, flow diagram 400B is implemented within acomputer system including a processor and memory coupled to theprocessor and having stored therein instructions that, if executed bythe computer system causes the system to execute the method for handingoff communications of at least one channel used by an ONU from thesource OLT to a destination OLT as implemented by the destination OLT.In still another embodiment, instructions for performing the method arestored on a non-transitory computer-readable storage medium havingcomputer-executable instructions for causing a computer system toperform the method for handing off communications of at least onechannel used by an ONU from the source OLT to a destination OLT asimplemented by the destination OLT. The operations of flow diagram 400Bare implemented within an OLT shown in FIGS. 1 and 2, in someembodiments of the present disclosure. In addition, flow diagram 400Bcan further describe one or more operations performed during the handingoff of an ONU from one OLT to another as described in the informationflow diagram 300 of FIG. 3. In addition, flow diagram 400B can beimplemented in conjunction with flow diagram 400A.

Flow diagram 400B discloses the process performed by a destination OLTwhen participating in handing off of communications of an ONU from asource OLT to the destination OLT. That is, instead of the source OLT,the destination OLT will be communicating with the ONU over thespecified transmitting channel (e.g., for downstream messaging) and/orreceiving channel (e.g., for upstream messages). The source OLT and thedestination OLT are communicatively coupled to a plurality of ONUsthrough a PON, though at a specific moment in time the source OLT andthe destination OLT can be coupled to different subsets of ONUs takenfrom the plurality.

In particular, the source OLT is configured to communicate over a firstchannel at a first wavelength of the PON. The destination OLT isconfigured to communicate over a second channel at a second wavelengthof the PON. For example, the first channel and the second channel can bedifferent combinations taken from an upstream channel and a downstreamchannel. In one implementation, the source OLT is communicating withONUs over a first channel that is a downstream channel, and thedestination OLT is communicating with ONUs over a second channel that isa downstream channel.

Flow diagram 400B is performed by the destination OLT during the handingoff of one or more wavelengths used to communicate with an ONU. At 450,the method includes receiving a notification message from the source OLTover a management channel of an inter-OLT communication network that afirst ONU will tune to the second channel at the second wavelengthassociated with the destination OLT. For example, the source OLT ishanding off to a destination OLT downstream communication to an ONU thatis currently being handled by the source OLT. In another example, thesource OLT is handing off to a destination OLT upstream communicationwith an ONU that is currently being handled by the source OLT. In stillanother example, the source OLT is handing off to a destination OLT bothupstream and downstream communication with an ONU that is currentlybeing handled by the source OLT. The destination OLT can also send anacknowledgment back to the source OLT indicating receipt of thenotification message.

As previously described, in one embodiment, the information necessary toimplement a handoff included within the notification message is providedin a data structure. For example, the notification message includes atleast one of the following: 1) a destination OLT identifier; 2) a sourceOLT identifier; and 3) an ONU identifier. In another embodiment, thenotification message can include additional information, including atleast one of the following: 1) the current downstream wavelength/channelfor the ONU; 2) the current upstream wavelength/channel for the ONU; 3)a possible new downstream wavelength/channel for the ONU; 4) a possiblenew upstream wavelength/channel for the ONU; 5) an ONU turning starttime; and 6) an acknowledge code.

At this point, during the handing off process, the destination OLT islooking for confirmation from the first ONU indicating completion of thehandoff of one or more channels from the source OLT to the destinationOLT. In particular, at 460, the method includes sending a handoff grantmessage from the destination OLT to the first ONU over the secondchannel.

For example, in one implementation, the source OLT is handing offdownstream communication with the first ONU, such that the destinationOLT will be sending downstream communications. In that case, thedestination OLT is configured to ping the first ONU using the handoffgrant message over the second channel, which is the downstream channelfor the destination OLT.

In another example, the source OLT is handing off upstream communicationwith the ONU, such that the destination OLT will be receiving upstreamcommunications from the first ONU. In that case, the first ONU can keepreceiving downstream communications from the source OLT. As such, thedestination OLT can send the handoff grant message through the sourceOLT, which acts as a proxy, as will be further described in FIG. 5.

At 470, the method includes receiving an acknowledgment from the firstONU over the second channel indicating receipt of the handoff grantmessage. In one embodiment, the handoff grant message is repeatedlydelivered until an acknowledgment is received from the first ONU. Atthis point, the destination OLT terminates the periodic delivery of thehandoff grant message.

In one embodiment, the handoff grant message is broadcast to a pluralityof ONUs through a corresponding ODN using a downstream channelassociated with the destination OLT and/or proxy OLT. The ONU intendedto receive the handoff grant message determines that the message istargeted to itself, as previously described.

FIG. 5 is an information flow diagram 500 showing the flow of messageswhen forwarding a message directed to an ONU from a first OLT to asecond OLT for delivery to the ONU, where the first OLT is unable tocommunicate with the ONU, in accordance with one embodiment of thepresent disclosure. For example, in a failover situation, the first OLTis unable to communicate over a downstream channel with the ONU, and hashanded off this responsibility to the second OLT. The first OLTcontinues to communicate with the ONU on an upstream wavelength. Thefirst OLT is able to communicate with the ONU using the second OLT as aproxy for delivering downstream messages to the OLT, such as managementand control PLOAM commands. In another example, a handoff process mayonly handoff one channel, such as a downstream channel. That is, thesource OLT has handed off the handling of downstream communications fromthe ONU to a destination OLT, but the source OLT still is handlingupstream communication from the ONU. In that case, the source OLT isunable to communicate directly (e.g., sending management and controlPLOAM commands) with the ONU on its downstream channel. As such, thesource OLT is able to use the destination OLT as a proxy to communicatewith the ONU. In still other embodiments, the process shown in FIG. 5can be adapted to deliver upstream communications from the ONU to thefirst OLT using the second OLT as a proxy, such as when the ONUcommunicates with the first OLT using a downstream channel, butcommunicates with the second OLT using the upstream channel.

Specifically, the messages shown in FIG. 5 are delivered between a firstOLT (e.g., source OLT), a second OLT (e.g., destination OLT), and anONU. The second OLT acts as a proxy for the first OLT for purposes ofdelivering downstream communications to the ONU. For example, the ONUupstream wavelength/channel is with the first OLT, and the ONUdownstream wavelength/channel is the second OLT. As a result, the secondOLT is configured to forward messages received from the first OLT to theONU using its downstream channel.

In one embodiment, some of the forwarded messages disclosed in FIG. 5conform with a PLOAM control message format. For example, the forwardedmessages could be control and management PLOAM messages, in oneembodiment. Of course, other embodiments are well suited to any suitableformat used for communicating control and management messages. Forexample, the forwarded messages can be an upstream transmissionopportunity assignment (such Bandwidth Map).

As shown in FIG. 5, at 505, the first OLT sends a forward request to thesecond OLT to deliver a message to the ONU. The forward request includesthe message to be forwarded, such as a control and/or management PLOAMmessage. For example, the first OLT can have handed off responsibilityof downstream communications with the ONU to the second OLT, but thefirst OLT is still communicating with the ONU over its upstream channel.In that case, the forwarding request is delivered from the first OLTover a management channel of an inter-OLT communication network to thesecond OLT.

At 510, the second OLT sends the forwarded message to the ONU using itsdownstream wavelength channel. In one embodiment, the forwarded messageis broadcast to a plurality of ONUs through a corresponding ODN. The ONUintended to receive the forwarded message determines that the message istargeted to itself.

At 515, after receiving the forwarded message from the second OLT, theONU can send a response to the first OLT. In the example shown in FIG.5, the first OLT is still communicating with the ONU using an upstreamwavelength/channel, and can receive upstream communications from theONU. In one implementation, the response is an acknowledgment messageconfirming receipt of the forwarded message.

In one embodiment, the information necessary to implement the forwardingprocess is provided in a data structure. For example, the forwardrequest message includes at least one of the following: 1) a first OLTidentifier; 2) a second OLT identifier; and 3) an ONU identifier. Inanother embodiment, the forward request includes additional information,including at least one of the following: 1) the to-be-forwarded message;and 2) the to-be-forwarded bandwidth map. For illustration, one exampleprovides using a source OLT as the first OLT, and the destination OLT asthe second OLT. The data structure provided in a request forward messagecan be structured as follows:

{ Destination OLT-ID, Source OLT-ID, ONU-ID, To-be-Forwarded PLOAMmessage, To-be-Forwarded Bandwidth Map, }

The inter-OLT communication shown in FIG. 5 can be used when initiallytuning or retuning of ONUs across one or more OLT ports. The inter-OLTcommunication is able to resolve differences in tuning used by differentcommunication formats, such as when resolving conflicts betweenpoint-to-point (PtP) WDM and TWDM-PON. In particular, when an ONU isfirst added to the ODN, it will go through a process of tuning itsreceiver to the first wavelength that it can find on the system. Aftertuning its receiver, it will begin the process of tuning thetransmitter, based on its knowledge of the receiver OLT retrieved fromthe channel announcement information embedded in the downstream frame.Methods to avoid PON disruption from unexpected ONU transfers whenhanding over ONUs can also be implemented through the process shown inFIG. 5. The OLT may not be able to communicate to the new ONU in theinitial stage, and as such, the inter-OLT communication protocol willthen enable the receiving OLT to report existence of the new ONU toother OLTs. In another case, the OLT (which can command the new ONU)would, in case of an ONU misbehavior, answer by trying to disable, park,or transition the ONU (transmitter or receiver or both) via re-tuning itto a different OLT port/channel pair. In still another case, when an ONUis associated with two OLTs (for example, its upstream is with OLT1 andits downstream is with OLT2), the inter-OLT communication protocolallows the upstream OLT (e.g., OLT1) to send messages via the downstreamOLT (e.g., OLT2) to the ONU. These types of inter-OLT collaborations areshown in FIG. 5. Various scenarios using inter-OLT communication aredescribed below, including ONU activation; parking orphaned ONUs; ONUsconnected to the wrong ODN; and rogue ONU isolation.

For ONU activation, discovery and ranging of ONUs can occur moreefficiently if an OLT port can communicate the proper associatedwavelength to use in upstream communication. When an ONU tunes to agiven wavelength, the receiving OLT first checks its provisioningdatabase and then queries other OLTs to determine the destinationwavelength of the ONU and passes the wavelength assignment to the ONU.The protocol facilitates communications between the OLTs to determinethe final destination of the ONU.

When parking orphaned ONUs, to prevent an ONU that is connected to thesystem and not assigned to any of the OLT ports from entering acontinuous tuning loop, the OLT will communicate with the rest of theOLT community to determine a final destination. If the ONU is notassigned to any OLTs, then it can be parked on the OLT until thewavelength assignment can be discovered, thereby substantiallyminimizing resource drain and potential rogue ONU activity.

In a case where an ONU is placed on the wrong ODN, the OLT chassis canquery the OLT chassis community and report the location of an ONU withrespect to ODN and system appearance. This facilitates more rapidtrouble resolution and helps the operator to resolve problems inactivating ONUs.

With so many wavelengths in use in a PON system and with the use oftunable technology, the risk of rogue ONUs potentially increases. When arogue ONU is present, the OLTs need to request assistance from the otherOLTs in the system to isolate the ONU. The process can include askingfor an “attendance report” between OLTs.

The aforementioned scenarios describe the inter-OLT communication on thesame ODN or across ODNs. It is important to identify the operationalsituations of these scenarios, since they determine at which “real time”degree the exchanges between OLTs occur. In back office cases, forexample operational situations include the following: system test in labenvironment (e.g., test in a PICS approach for tuning/re-tuningoperations qualification); reduction of the number of active ports(e.g., in a pay as you go context); operating expenses (OPEX) savingsthrough temporary shutdown of underused OLT ports for power savings; andplanned maintenance operations. In front office cases, for exampleoperational situations include the following: adding an additional ONU(e.g., in self install context, or by technician intervention); ONUwake-up after a sleep period, which can depend on ONU transceiver (TRx)drift; and troubleshooting. In one implementation, inter-OLT exchangesoccur in a time period sufficient to allow resumption of full operationwithin an acceptable period.

FIG. 6 is a diagram 600 illustrating the distribution of a host masterclock 610 to a plurality of OLTs (e.g., OLTa-n) within a central office,in accordance with one embodiment of the present disclosure. The OLTsare associated with a plurality of slave clocks 630. As shown in FIG. 6,the host master clock 610 generates a clock signal 650 at output 640.The clock signal 650 is copied and distributed over multiple channelsover logical connections to the OLTs. In that manner, the slave clockfor each OLT is timed using the copied clock signal 650. In oneimplementation, intra-OLT cable differences can be about 100 meters, andthe actual time difference between OLTs is around +/−2 μs.

In one embodiment, it is necessary to provide a reasonable quiet windowalignment across all OLT ports operating on a given ODN. When severalOLT chassis are used to implement a TWDM-PON system, time of day (ToD)and phase synchronization through SNI interfaces is mandatory.Synchronization is provided through the master clock. That is, themaster clock is used to synchronize OLT quiet windows. Synchronizationof the quiet windows among all OLTs sharing the same ODN minimizesdisruption caused on a given OLT port by ONUs attempting to activate. Inparticular, utilizing the inter-OLT communication protocol, detailsabout the quiet window can be shared among the OLTs. The OLTs can verifytheir timing source and the timing of their quiet window. The OLTs cannegotiate changes in the timing window. A common reference frame forsynchronization substantially minimizes the tuning/ranging for ONUs andOLTs, and thus upstream jitter is reduced, especially for mobileapplications.

FIG. 7 is a table 700 illustrating exemplary ONU data elements that arepassed using the inter-OLT communications protocol. FIG. 8 is a table800 illustrating exemplary OLT data elements that are passed using theinter-OLT communications protocol. FIG. 9 is a table 900 providing alist of exemplary state change requests and notifications used by theinter-OLT communications protocol.

Several NG-PON2 transmission convergence (TC) layer functions requireinteraction between the NG-PON2 channel terminations (CTs) via theInter-CT Protocol. For the TWDM CTs, these functions include, forexample, the following: channel profile and status sharing; ONUactivation; ONU tuning; and rogue ONU mitigation. Furthermore, thefunction of rogue ONU mitigation can require interaction between TWDMCTs and PtP WDM CTs. The NG-PON2 TC layer procedures implementing thesefunctions interface with the ICT Protocol by means of ICTP Primitives.There are two types of ICTP primitives: transaction commits andmessages. A transaction itself is composed of lower level messageexchanges and is treated as an atomic operation. Invocations of ICTPprimitives by the TC layer procedures have the following format:ICTP:<Name> (ODN ID, source (SRC), destination (DST), Parameters). FIG.10 is a table 1000 illustrating exemplary ICTP protocol primitiveinvocation format elements. FIG. 11 is a table 1100 illustratingexemplary ICTP protocol primitives.

Thus, according to embodiments of the present disclosure, systems andmethods are described for providing an inter-OLT communication protocol,involving data structures, to manage the discovery and transition ofONUS.

While the foregoing disclosure sets forth various embodiments usingspecific block diagrams, flowcharts, and examples, each block diagramcomponent, flowchart step, operation, and/or component described and/orillustrated herein may be implemented, individually and/or collectively,using a wide range of hardware, software, or firmware (or anycombination thereof) configurations. In addition, any disclosure ofcomponents contained within other components should be considered asexamples because many other architectures can be implemented to achievethe same functionality.

The process parameters and sequence of steps described and/orillustrated herein are given by way of example only and can be varied asdesired. For example, while the steps illustrated and/or describedherein may be shown or discussed in a particular order, these steps donot necessarily need to be performed in the order illustrated ordiscussed. The various example methods described and/or illustratedherein may also omit one or more of the steps described or illustratedherein or include additional steps in addition to those disclosed.

While various embodiments have been described and/or illustrated hereinin the context of fully functional computing systems, one or more ofthese example embodiments may be distributed as a program product in avariety of forms, regardless of the particular type of computer-readablemedia used to actually carry out the distribution. The embodimentsdisclosed herein may also be implemented using software modules thatperform certain tasks. These software modules may include script, batch,or other executable files that may be stored on a computer-readablestorage medium or in a computing system. These software modules mayconfigure a computing system to perform one or more of the exampleembodiments disclosed herein. One or more of the software modulesdisclosed herein may be implemented in a cloud computing environment.Cloud computing environments may provide various services andapplications via the Internet. These cloud-based services (e.g.,software as a service, platform as a service, infrastructure as aservice, etc.) may be accessible through a Web browser or other remoteinterface. Various functions described herein may be provided through aremote desktop environment or any other cloud-based computingenvironment.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions, andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Manymodifications and variations are possible in view of the aboveteachings. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical applications,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as may besuited to the particular use contemplated.

Embodiments according to the present disclosure are thus described.While the present disclosure has been described in particularembodiments, it should be appreciated that the disclosure should not beconstrued as limited by such embodiments, but rather construed accordingto the below claims.

What is claimed is:
 1. An apparatus for communications in a passiveoptical network (PON) system, the apparatus comprising: a memory storagecomprising instructions; and a processor in communication with thememory storage and configured to execute the instructions to: performcommunication exchanges between a first OLT port device of the PONsystem and a second OLT port device of the PON system, with theprocessor exchanging a message between the first OLT port device and thesecond OLT port device, the message being associated with an opticalnetwork unit (ONU), with the message comprising: a source identifiercomprising a first PON identifier (PON ID) identifying a source OLT portdevice that sends the message, wherein the source OLT port device isconfigured to communicate over a first channel pair at a firstwavelength pair of the PON system; a destination identifier comprising asecond PON ID identifying a destination OLT port device that receivesthe message or comprising an identifier designated to multiple OLT portdevices, wherein the destination OLT port device is configured tocommunicate over a second channel pair at a second wavelength pair ofthe PON system; and an ONU identifier associated with the ONU.
 2. Theapparatus of claim 1, wherein the message indicates that the ONU tunesto at least one channel of the second channel pair associated with thedestination OLT port device.
 3. The apparatus of claim 1, with theprocessor coupled to the source OLT port device, with the message beingsent from source OLT port device to the destination OLT port device,wherein the processor is further configured to receive a firstacknowledgment sent by the destination OLT port device, the firstacknowledgement indicating receipt of the message, and wherein theprocessor is further configured to receive a second acknowledgment sentby the ONU, the second acknowledgement indicating receipt of a tunewavelength message that is sent by the source OLT port device.
 4. Theapparatus of claim 1, wherein the message comprises at least part of aphysical layer operations administration maintenance (PLOAM) message. 5.The apparatus of claim 4, wherein the message further comprises ONUchannel information indicating at least one of an ONU current upstreamwavelength or channel (wavelength/channel), an ONU current downstreamwavelength/channel, an ONU new upstream wavelength/channel, or an ONUnew downstream wavelength/channel.
 6. The apparatus of claim 4, with theprocessor coupled to the destination OLT port device, with the messagereceived from the source OLT port device via the destination OLT portdevice, and wherein the processor is further configured to cause thedestination OLT port device to send at least part of the message to theONU over a downstream channel of the second channel pair.
 7. Theapparatus of claim 1, wherein the processor is further configured tocause the source OLT port device to send a tune wavelength message tothe ONU over a downstream channel of the first channel pair, with thetune wavelength message instructing the ONU to tune to at least onechannel of the second channel pair.
 8. The apparatus of claim 1, whereinthe processor is configured to communicate between the first OLT portdevice and the second OLT port device via a management channel of acommunication network.
 9. A non-transitory computer-readable mediastoring computer instructions, that when executed by one or moreprocessors, cause the one or more processors to perform the steps of:performing communication exchanges between a first OLT port device of apassive optical network (PON) system and a second OLT port device of thePON system, with the communication exchanges between the first OLT portdevice and the second OLT port device comprising receiving or sending amessage associated with an optical network unit (ONU), with the messagecomprising: a source identifier comprising a first PON identifier (PONID) identifying a source OLT port device that sends the message, whereinthe source OLT port device is configured to communicate over a firstchannel pair at a first wavelength pair of the PON system; a destinationidentifier comprising a second PON ID identifying a destination OLT portdevice that receives the message or comprising an identifier designatedto multiple OLT port devices, wherein the destination OLT port device isconfigured to communicate over a second channel pair at a secondwavelength pair of the PON system; and an ONU identifier associated withthe ONU.
 10. The non-transitory computer-readable media of claim 9,wherein the message indicates that the ONU tunes to at least one channelof the second channel pair associated with the destination OLT portdevice.
 11. The non-transitory computer-readable media of claim 9,wherein the steps further comprise: receiving a first acknowledgmentthat is sent by the destination OLT port device, with the firstacknowledgment indicating receipt of the message, and receiving a secondacknowledgment sent by the ONU, with the second acknowledgmentindicating receipt of a tune wavelength message sent by the source OLTport device.
 12. The non-transitory computer-readable media of claim 9,wherein the message comprises at least part of a physical layeroperations administration maintenance (PLOAM) message.
 13. Thenon-transitory computer-readable media of claim 12, wherein the messagefurther comprises ONU channel information indicating at least one of anONU current upstream wavelength or channel (wavelength/channel), an ONUcurrent downstream wavelength/channel, an ONU new upstreamwavelength/channel, or an ONU new downstream wavelength/channel.
 14. Thenon-transitory computer-readable media of claim 12, wherein the stepscomprise: causing the destination OLT port device to send at least partof the message to the ONU over a downstream channel of the secondchannel pair.
 15. The non-transitory computer-readable media of claim 9,wherein the steps comprise: causing the source OLT port device to send atune wavelength message to the ONU over a downstream channel of thefirst channel pair, with the tune wavelength message instructing the ONUto tune to at least one channel of the second channel pair.
 16. Thenon-transitory computer-readable media of claim 9, wherein the stepscomprise: communicating between the first OLT port device and the secondOLT port device via a management channel of a communication network. 17.A method for communications in a passive optical network (PON) system,the method comprising: performing, by a first OLT port device of the PONsystem, communication exchanges with a second OLT port device of the PONsystem, with the communication exchanges comprising sending by the firstOLT port device to the second OLT port device or receiving by the firstOLT port device from the second OLT port device a message associatedwith an optical network unit (ONU), with the message comprising: asource identifier comprising a first PON identifier (PON ID) identifyinga source OLT port device that sends the message, wherein the source OLTport device is configured to communicate over a first channel pair at afirst wavelength pair of the PON system; a destination identifiercomprising a second PON ID identifying a destination OLT port devicethat receives the message or an identifier designated to multiple OLTport devices, wherein the destination OLT port device is configured tocommunicate over a second channel pair at a second wavelength pair ofthe PON system; and an ONU identifier associated with the ONU.
 18. Themethod of claim 17, wherein the message comprises at least part of aphysical layer operations administration maintenance (PLOAM) message.19. The method of claim 18, wherein the message further comprises ONUchannel information indicating at least one of an ONU current upstreamwavelength or channel (wavelength/channel), an ONU current downstreamwavelength/channel, an ONU new upstream wavelength/channel, or an ONUnew downstream wavelength/channel.
 20. The method of claim 17, with thefirst OLT port device comprising the source OLT port device, the methodfurther receiving a first acknowledgment sent by the destination OLTport device, with the first acknowledgment indicating receipt of themessage, and receiving a second acknowledgment sent by the ONU, with thesecond acknowledgment indicating receipt of a tune wavelength messagethat is sent by the source OLT port device.